A. When you use RDP to communicate with hosts, there are times when the same bitmap is repeatedly required on the client. Instead of repeatedly sending the same image to be rendered, the server sends the bitmap once and tells the client to cache the bitmap in an uncompressed form. This cached copy goes in RAM and, optionally, to persists (is stored) on disk so it can be used in future sessions. This cache consists of several large BMC files that are stored under %USERPROFILE%\AppData\Local\Microsoft\Terminal Server Client\Cache. You could delete them, but unless you have a real disk space problem I'd advise against it.
You can move this cache if you want by navigating to HKEY_CURRENT_USER\Software\Microsoft\Terminal Server Client using RegEdit and creating a new String value named BitmapPersistCacheLocation. Set this value to the location where the bitmap cache files should be stored.